#include<iostream>
using namespace std;
typedef long long LL;
int n;
bool prime(LL x)
{
	for (LL i = 2; i * i <= x; i++) {
		if (x % i) {
			return 0;
		}
	}
	return 1;
}
LL gcd(LL a, LL b)
{
	return b ? gcd(b, a % b) : a;
}
int main()
{
	/*LL ans = 0;
	cin >> n;
	int flag = 0;
	for (LL i = n; i; i--) {
		if (prime(i)) {
			ans += i;
			flag++;
			if (flag == 2) {
				break;
			}
		}
	}
	cout << ans << endl;*/
	cin >> n;
	if (n == 1) {
		cout << 2 << endl;
		return 0;
	}
	cout << n + n - 1 << endl;
	return 0;
}